Congratulations - you bricked it. The fancy Mod wants you to spend a fortune being online all the time or the phone won't work so you need to put it back the way it was when you bought it.
Turn it off then hold down the Volume Up button while pressing the Power button to start it it up. A menu appears and you need to scroll up and nown the menu with the Volume buttons and get to Factory Reset or similar by pressing the power button to select it.
You'll lose any personal data but the phone should work again.